Public Information Statement
Issued by NWS Caribou, ME
NOUS41 KCAR 181218
PUBLIC INFORMATION STATEMENT
NATIONAL WEATHER SERVICE CARIBOU ME
818 AM EDT MON JUL 18 2016
...HURRICANE PREPAREDNESS WEEK 2016...
TROPICAL STORMS AND HURRICANES
The term "tropical cyclone" is a generic name given to a low
pressure system that generally forms in the tropics and is
accompanied by showers and thunderstorms and a
counterclockwise wind circulation. Depending on the strength
of the winds in the circulation, tropical cyclones are
further divided into tropical depressions, tropical storms,
The tropical cyclones that affect eastern North America
generally form in either the tropical Atlantic Ocean, the
Caribbean Sea, or in the Gulf of Mexico. The three main
conditions which favor tropical cyclone development are (1)
warm ocean waters, (2) atmospheric moisture, and (3)
relatively light winds aloft. In addition, an atmospheric
disturbance, called a tropical wave, is needed to initiate
the development the counter-clockwise wind circulation. If
the favorable conditions persist for a sufficient amount of
time, the tropical disturbance can strengthen to a TROPICAL
DEPRESSION, TROPICAL STORM, or HURRICANE. When the winds in
a tropical cyclone reach tropical storm strength (39 mph, 34
kt), the storm is "named". Tropical cyclones are classified
Tropical Cyclone Terms:
Tropical Depression - An organized system of clouds and
thunderstorms with a defined surface circulation and maximum
sustained winds of 38 mph (33 knots) or less.
Tropical Storm - An organized system of strong thunderstorms
with a defined surface circulation and maximum sustained
winds of 39-73 mph (34-63 knots).
Hurricane - An intense tropical weather system of strong
thunderstorms with a well-defined surface circulation and
maximum sustained winds of 74 mph (64 knots) or higher.
Hurricanes are also classified into different categories
based on strength.
Tropical Cyclone Description:
The well-developed hurricane consists of an eye, an eyewall,
and spiral bands of showers and thunderstorms. In the eye,
winds are relative calm and there is a gentle sinking motion
in the atmosphere which leads to mostly clear skies.
Surrounding the eye is the eyewall which contains the most
violent winds, the most intense showers and thunderstorms in
the hurricane, and can contain tornadoes. The winds in the
eyewall also have the greatest potential for causing a deadly
storm surge. Outside the eyewall, spiral bands of showers
and thunderstorms rotate around the storm. These bands of
showers and thunderstorms can also be very intense, can move
into an area very rapidly, and are the most likely area in
the hurricane for tornadoes to form.
Tropical Cyclone Threats:
Hurricanes and tropical storms bring with them four main
threats: high winds, coastal storm surge, inland fresh water
flooding, and tornadoes. These will be discussed in greater
detail in forthcoming statements.
While hurricane season lasts from June through November, the
peak of the season is from mid-August through October. Each
year, an average of ten tropical storms develop over the
Atlantic Ocean, Caribbean Sea, and Gulf of Mexico. Many of
these storms remain over the ocean, and an average of six of
these storms become hurricanes each year. During an average
3-year period, roughly five hurricanes strike the United
States coastline, killing approximately 45 people (an average
of 15.5 per year) anywhere from Texas to Maine. Of these, two
are typically "major" or "intense" hurricanes (winds greater
than 110 mph).
Now is the time to prepare for Hurricanes and Tropical Storms: